Hand-rotatable bicycle gear shifters have been developed as replacements for the older lever-actuated shifters, especially for use in conjunction with off-road or "mountain" bicycles. Hand-rotatable shift actuators are disclosed, for example, in U.S. Pat. No. 4,900,291 issued Feb. 13, 1990; U.S. Pat. No. 4,938,733 issued Jul. 3, 1990; U.S. Pat. No. 5,102,372 issued Apr. 7, 1992; and U.S. Pat. No. 5,197,927 issued Mar. 30, 1993. All of these patents are assigned to the assignee of this application. In each of the foregoing patents, a bicycle derailleur is actuated by a rotatable grip which is located on the handlebar of the bicycle inboard of the normal handgrip. Prior to this invention, the gripping surface of rotatable grips sold by the assignee of this application was typically formed of foam rubber or neoprene, was secured to an underlying rotatable member of the gear shifter assembly, and typically had a smooth outer surface.
The assignee has experimented with hand-rotatable grips with axially extending ribs where the grips were formed of a hard plastic material such as ABS; these grips were less than optimal in that they presented harsh sharp edges to the operator's hand. These edges were uncomfortable to the rider especially in those conditions involving uneven surfaces, as occasionally experienced on most roads but presenting an especially acute problem for off-the-road bicycle travel. Also, these prior rotatable grips of the assignee tended to become slippery when fouled by mud and the like, reducing the amount of torque capable of being applied by the rider. A need therefore exists for improved grips with optimum torque-transmission and antifouling features which are adapted to be incorporated into a hand-rotatable gear shifter.